Type Checking Research Articles

Combining Type Checking and Set Constraint Solving to Improve Automated Software Verification

Abstract This technical note shows how we have combined prescriptive type checking and constraint solving to increase automation during software verification. We do so by defining a type system and implementing a typechecker for $\{log\}$ (read ‘setlog’), a Constraint Logic Programming language and satisfiability solver based on set theory. The constraint solver is proved to be safe w.r.t. the type system. Two industrial-strength case studies are presented where this combination is used with very good results.

Atrasentan in Patients with IgA Nephropathy.

Patients with IgA nephropathy and severe proteinuria have a high lifetime risk of kidney failure. The efficacy and safety of the selective endothelin type A receptor antagonist atrasentan in reducing proteinuria in patients with IgA nephropathy are incompletely understood. We are conducting a phase 3, multinational, double-blind, randomized, controlled trial involving adults with biopsy-proven IgA nephropathy, a total urinary protein excretion of at least 1 g per day, and an estimated glomerular filtration rate of at least 30 ml per minute per 1.73 m2 of body-surface area. Patients were randomly assigned to receive atrasentan (0.75 mg per day) or matched placebo for 132 weeks. The primary outcome, assessed at a prespecified interim analysis of data from the first 270 patients in the main stratum, was the change in the 24-hour urinary protein-to-creatinine ratio from baseline to week 36; the change was estimated with the use of a repeated-measures model. (An exploratory stratum of patients who were receiving a sodium-glucose cotransporter 2 inhibitor were included in a separate analysis.) Safety analyses were based on adverse events across the entire main stratum. A total of 340 patients were recruited into the main stratum. Among the first 270 patients in the main stratum (135 per trial group) who completed the week 36 visit, the geometric mean percentage change in the urinary protein-to-creatinine ratio relative to baseline was significantly greater with atrasentan (-38.1%) than with placebo (-3.1%), with a geometric mean between-group difference of -36.1 percentage points (95% confidence interval, -44.6 to -26.4; P<0.001). The percentage of patients with adverse events did not differ substantially between the two groups. Fluid retention was reported by 19 of 169 patients (11.2%) in the atrasentan group and in 14 of 170 (8.2%) in the placebo group but did not lead to discontinuation of the trial regimen. No apparent cases of cardiac failure or severe edema occurred. In this prespecified interim analysis, atrasentan resulted in a significant and clinically meaningful reduction in proteinuria as compared with placebo in patients with IgA nephropathy. (Funded by Novartis; ALIGN ClinicalTrials.gov number, NCT04573478.).

Refinement Type Refutations

Refinement types combine SMT decidable constraints with a compositional, syntax-directed type system to provide a convenient way to statically and automatically check properties of programs. However, when type checking fails, programmers must use cryptic error messages that, at best, point out the code location where a subtyping constraint failed to determine the root cause of the failure. In this paper, we introduce refinement type refutations, a new approach to explaining why refinement type checking fails, which mirrors the compositional way in which refinement type checking is carried out. First, we show how to systematically transform standard bidirectional type checking rules to obtain refutations. Second, we extend the approach to account for global constraint-based refinement inference via the notion of a must-instantiation: a set of concrete inhabitants of the types of subterms that suffice to demonstrate why typing fails. Third, we implement our method in HayStack—an extension to LiqidHaskell which automatically finds type-refutations when refinement type checking fails, and helps users understand refutations via an interactive user-interface. Finally, we present an empirical evaluation of HayStack using the regression benchmark-set of LiqidHaskell, and the benchmark set of G2, a previous method that searches for (non-compositional) counterexample traces by symbolically executing Haskell source. We show that HayStack can find refutations for 99.7% of benchmarks, including those with complex typing constructs (e.g., abstract and bounded refinements, and reflection), and does so, an order of magnitude faster than G2.

Imperative Compositional Programming: Type Sound Distributive Intersection Subtyping with References via Bidirectional Typing

Compositional programming is a programming paradigm that emphasizes modularity and is implemented in the CP programming language. The foundations for compositional programming are based on a purely functional variant of System F with intersection types, called Fi+, which includes distributivity rules for subtyping. This paper shows how to extend compositional programming and CP with mutable references, enabling a modular, imperative compositional programming style. A technical obstacle solved in our work is the interaction between distributive intersection subtyping and mutable references. Davies and Pfenning [2000] studied this problem in standard formulations of intersection type systems and argued that, when combined with references, distributive subtyping rules lead to type unsoundness. To recover type soundness, they proposed dropping distributivity rules in subtyping. CP cannot adopt this solution, since it fundamentally relies on distributivity for modularity. Therefore, we revisit the problem and show that, by adopting bidirectional typing, a more lightweight and type sound restriction is possible: we can simply restrict the typing rule for references. This solution retains distributivity and an unrestricted intersection introduction rule. We present a first calculus, based on Davies and Pfenning's work, which illustrates the generality of our solution. Then we present an extension of Fi+ with references, which adopts our restriction and enables imperative compositional programming. We implement an extension of CP with references and show how to model a modular live-variable analysis in CP. Both calculi and their proofs are formalized in the Coq proof assistant.

CoolerSpace: A Language for Physically Correct and Computationally Efficient Color Programming

Color programmers manipulate lights, materials, and the resulting colors from light-material interactions. Existing libraries for color programming provide only a thin layer of abstraction around matrix operations. Color programs are, thus, vulnerable to bugs arising from mathematically permissible but physically meaningless matrix computations. Correct implementations are difficult to write and optimize. We introduce CoolerSpace to facilitate physically correct and computationally efficient color programming. CoolerSpace raises the level of abstraction of color programming by allowing programmers to focus on describing the logic of color physics. Correctness and efficiency are handled by CoolerSpace. The type system in CoolerSpace assigns physical meaning and dimensions to user-defined objects. The typing rules permit only legal computations informed by color physics and perception. Along with type checking, CoolerSpace also generates performance-optimized programs using equality saturation. CoolerSpace is implemented as a Python library and compiles to ONNX, a common intermediate representation for tensor computations. CoolerSpace not only prevents common errors in color programming, but also does so without run-time overhead: even unoptimized CoolerSpace programs out-perform existing Python-based color programming systems by up to 5.7 times; our optimizations provide up to an additional 1.4 times speed-up.

A Dependent Nominal Physical Type System for Static Analysis of Memory in Low Level Code

We tackle the problem of checking non-proof-carrying code , i.e. automatically proving type-safety (implying in our type system spatial memory safety) of low-level C code or of machine code resulting from its compilation without modification. This requires a precise static analysis that we obtain by having a type system which (i) is expressive enough to encode common low-level idioms, like pointer arithmetic, discriminating variants by bit-stealing on aligned pointers, storing the size and the base address of a buffer in distinct parts of the memory, or records with flexible array members, among others; and (ii) can be embedded in an abstract interpreter. We propose a new type system that meets these criteria. The distinguishing feature of this type system is a nominal organization of contiguous memory regions, which (i) allows nesting, concatenation, union, and sharing parameters between regions; (ii) induces a lattice over sets of addresses from the type definitions; and (iii) permits updates to memory cells that change their type without requiring one to control aliasing. We provide a semantic model for our type system, which enables us to derive sound type checking rules by abstract interpretation, then to integrate these rules as an abstract domain in a standard flow-sensitive static analysis. Our experiments on various challenging benchmarks show that semantic type-checking using this expressive type system generally succeeds in proving type safety and spatial memory safety of C and machine code programs without modification, using only user-provided function prototypes.

On the Expressive Power of Languages for Static Variability

Variability permeates software development to satisfy ever-changing requirements and mass-customization needs. A prime example is the Linux kernel, which employs the C preprocessor to specify a set of related but distinct kernel variants. To study, analyze, and verify variational software, several formal languages have been proposed. For example, the choice calculus has been successfully applied for type checking and symbolic execution of configurable software, while other formalisms have been used for variational model checking, change impact analysis, among other use cases. Yet, these languages have not been formally compared, hence, little is known about their relationships. Crucially, it is unclear to what extent one language subsumes another, how research results from one language can be applied to other languages, and which language is suitable for which purpose or domain. In this paper, we propose a formal framework to compare the expressive power of languages for static (i.e., compile-time) variability. By establishing a common semantic domain to capture a widely used intuition of explicit variability, we can formulate the basic, yet to date neglected, properties of soundness, completeness, and expressiveness for variability languages. We then prove the (un)soundness and (in)completeness of a range of existing languages, and relate their ability to express the same variational systems. We implement our framework as an extensible open source Agda library in which proofs act as correct compilers between languages or differencing algorithms. We find different levels of expressiveness as well as complete and incomplete languages w.r.t. our unified semantic domain, with the choice calculus being among the most expressive languages.

Making Formulog Fast: An Argument for Unconventional Datalog Evaluation

With its combination of Datalog, SMT solving, and functional programming, the language Formulog provides an appealing mix of features for implementing SMT-based static analyses (e.g., refinement type checking, symbolic execution) in a natural, declarative way. At the same time, the performance of its custom Datalog solver can be an impediment to using Formulog beyond prototyping—a common problem for Datalog variants that aspire to solve large problem instances. In this work we speed up Formulog evaluation, with some surprising results: while 2.2× speedups can be obtained by using the conventional techniques for high-performance Datalog (e.g., compilation, specialized data structures), the big wins come by abandoning the central assumption in modern performant Datalog engines, semi-naive Datalog evaluation. In the place of semi-naive evaluation, we develop eager evaluation, a concurrent Datalog evaluation algorithm that explores the logical inference space via a depth-first traversal order. In practice, eager evaluation leads to an advantageous distribution of Formulog’s SMT workload to external SMT solvers and improved SMT solving times: our eager evaluation extensions to the Formulog interpreter and Soufflé’s code generator achieve mean 5.2× and 7.6× speedups, respectively, over the optimized code generated by off-the-shelf Soufflé on SMT-heavy Formulog benchmarks. All in all, using compilation and eager evaluation (as appropriate), Formulog implementations of refinement type checking, bottom-up pointer analysis, and symbolic execution achieve speedups on 20 out of 23 benchmarks over previously published, hand-tuned analyses written in F ♯ , Java, and C++, providing strong evidence that Formulog can be the basis of a realistic platform for SMT-based static analysis. Moreover, our experience adds nuance to the conventional wisdom that traditional semi-naive evaluation is the one-size-fits-all best Datalog evaluation algorithm for static analysis workloads.

Law and Order for Typestate with Borrowing

Typestate systems are notoriously complex as they require sophisticated machinery for tracking aliasing. We propose a new, transition-oriented foundation for typestate in the setting of impure functional programming. Our approach relies on ordered types for simple alias tracking and its formalization draws on work on bunched implications. Yet, we support a flexible notion of borrowing in the presence of typestate. Our core calculus comes with a notion of resource types indexed by an ordered partial monoid that models abstract state transitions. We prove syntactic type soundness with respect to a resource-instrumented semantics. We give an algorithmic version of our type system and prove its soundness. Algorithmic typing facilitates a simple surface language that does not expose tedious details of ordered types. We implemented a typechecker for the surface language along with an interpreter for the core language.

Main heat transport system configuration influence on steam drum level control and safety for a pressure tube type boiling water reactor with multiple interconnected loops

Abstract NCABWR (Natural-Circulation-Advanced-Boiling-Water-Reactor) is a pressure-tube-type BWR with multiple inter-connected Main-Heat-Transport (MHT) system loops and steam drums (SDs). SD-Level-Control is related to, the MHT coolant inventory and sustained heat removal, hence the overall safety of the Nuclear-Power-Plant (NPP). SD-Level is vital for ensuring presence of adequate coolant-inventory with sufficient and prolonged cooling of fuel, for normal-operation and accidents. In the initial-MHT-configuration of NCABWR the four MHT-loops are, inter-connected at the Common-Reactor-Inlet-Header (CRIH), which influences the SDLC adversely; such occurrences are, not reported in the open literature. Open loop (without SD-level-controllers) step-change response showed that initial MHT-configuration response is stable, non-oscillatory and non-diverging even for a high-magnitude step-change in the feed-flows. Closed-loop (with SD-level-controllers) response, even to minor disturbances leads to diverging SD-Levels due to CRIH-MHT-configuration (Gaikwad, A.J., Vijayan, P., Iyer, K., Bhartiya, S., Kumar, R., Lele, H.G., Ghosh, A.K., Kushwaha, H.S., and Sinha, R.K. (2009). Effect of loop configuration on steam drum level control for a multiple drum interconnected loops pressure tube type boiling water reactor. IEEE Trans. Nucl. Sci. 56: 3712–3725). CRIH is required to overcome Postulated-Initiating-Event (PIE) for single-accumulator-failure-LOCA. A hypothetical MHT-configuration with partitioning of CRIH will isolate each loop from one another and lead to a stable SDLC, but then for the above-mentioned PIE safety is not met. LOCA in one of the four ECCS header-compartments require a mandatory interconnection among, the four MHT-Loops at CRIH. Solution to SDLC issue were explored with changes in MHT-configuration and with innovative solution-schemes for feed-water-system and SDLCs. In the present study the pioneering solution-schemes with individual SD pressure control for SD level control and the Split/Double baffle are proposed, implemented and the performance was tested with simulation are discussed in details with other solution schemes.

Higher-Order Asynchronous Effects

We explore asynchronous programming with algebraic effects. We complement their conventional synchronous treatment by showing how to naturally also accommodate asynchrony within them, namely, by decoupling the execution of operation calls into signalling that an operation's implementation needs to be executed, and interrupting a running computation with the operation's result, to which the computation can react by installing interrupt handlers. We formalise these ideas in a small core calculus and demonstrate its flexibility using examples ranging from a multi-party web application, to pre-emptive multi-threading, to (cancellable) remote function calls, to a parallel variant of runners of algebraic effects. In addition, the paper is accompanied by a formalisation of the calculus's type safety proofs in Agda, and a prototype implementation in OCaml.

Volatilomics: An emerging discipline within Omics Sciences - A systematic review

Introduction Volatilomics is an omics science that is characterized as being a specific subbranch of metabolomics, which studies the different types of volatile organic compounds that may be present in a certain biological matrix. It has had impacts on the identification of new natural compounds and food safety processes, since it allows the evaluation of emerging contaminants that are present on food matrices, through the identification of biomarkers generated in response to this type of xenobiotic compounds through xenovolatilomic studies. Objective In this way, this review seeks to understand the scientific advances reported towards volatilomic studies, for which different types of primary research are reported depending on the main instrumental techniques used for the characterization of different types of VOCs that have been reported in our country between 2012 and 2022. Methodology Using a qualitative methodology, a search was carried out in the Scopus database, from which the bibliometric information of the primary research reported during this time was obtained, to later analyze the different research concerning the use of volatilomic studies and the fields of action that are currently used, as well as the different techniques for obtaining these compounds and the data analysis methodologies established for the processing of this type of research. Conclusions Finally, it can be concluded that, from the present review, the applicability of volatilomic studies is shown. The incursion carried out by this type of science on the verification of food safety in different types of matrices, in addition to allowing the study of the volatile profile formed by the different volatile organic compounds expressed by said matrix and the respective ecological role expressed by these compounds with the environment in which they are found.

12-year effectiveness and safety of botulinum toxin type A for the treatment of blepharospasm and hemifacial spasm

12-year effectiveness and safety of botulinum toxin type A for the treatment of blepharospasm and hemifacial spasm

Assessing the efficacy and quality of Life improvements of botulinum toxin type a with topical minoxidil versus topical minoxidil in male androgenetic alopecia: a randomized controlled trial.

Androgenetic alopecia (AGA) is a common type of hair loss in men and efficacy and safety of current medical treatment remain limited. Therefore, the present study aimed to investigate the efficacy and safety of botulinum toxin type A (BTA) combined with Minoxidil in patients with AGA. 60 male patients were included in this study and control group received topical 5% Minoxidil and the treatment group received BTA combined with topical 5% Minoxidil. BTA injections (60-70 U) were administered at 30-35 scalp sites. Head photographs were taken at baseline, 2nd, 4th, and 6th months. Clinical descriptions recorded scalp conditions, and patient satisfaction along with Dermatology Life Quality Index scores were documented. The treatment group (TG) showed significant hair growth differences compared to the control group (CG) at the 4th month (P < 0.001) and 6th month (P = 0.0046) post-treatment. TG had improved Investigator Global Assessment (IGA) scores in the 4th month (P = 0.0001) and 6th month (P = 0.0259) compared to CG. Patient satisfaction in TG for hair growth and scalp improvement was higher than CG (all P < 0.05). TG exhibited substantial quality of life improvement at the 4-month (P = 0.0009) and 6-month (P = 0.0099). No adverse reactions were observed post-botulinum toxin injection. BTA combined with Minoxidil effectively promotes hair growth, enhances the quality of life, and alleviates scalp symptoms in male AGA patients at 4th and 6th months, with no adverse effects compared to Minoxidil alone.Trial registration number: Ethics Committee of Shanghai Tongji Hospital (ID: K-2018-026).

Automated Verification of Higher-Order Probabilistic Programs via a Dependent Refinement Type System

Verification of higher-order probabilistic programs is a challenging problem. We present a verification method that supports several quantitative properties of higher-order probabilistic programs. Usually, extending verification methods to handle the quantitative aspects of probabilistic programs often entails extensive modifications to existing tools, reducing compatibility with advanced techniques developed for qualitative verification. In contrast, our approach necessitates only small amounts of modification, facilitating the reuse of existing techniques and implementations. On the theoretical side, we propose a dependent refinement type system for a generalised higher-order fixed point logic (HFL). Combined with continuation-passing style encodings of properties into HFL, our dependent refinement type system enables reasoning about several quantitative properties, including weakest pre-expectations, expected costs, moments of cost, and conditional weakest pre-expectations for higher-order probabilistic programs with continuous distributions and conditioning. The soundness of our approach is proved in a general setting using a framework of categorical semantics so that we don’t have to repeat similar proofs for each individual problem. On the empirical side, we implement a type checker for our dependent refinement type system that reduces the problem of type checking to constraint solving. We introduce admissible predicate variables and integrable predicate variables to constrained Horn clauses (CHC) so that we can soundly reason about the least fixed points and samplings from probability distributions. Our implementation demonstrates that existing CHC solvers developed for non-probabilistic programs can be extended to a solver for the extended CHC with only small efforts. We also demonstrate the ability of our type checker to verify various concrete examples.

Staged Compilation with Module Functors

Multi-stage programming has been used in a wide variety of domains to eliminate the tension between abstraction and performance. However, the interaction of multi-stage programming features with features for programming-in-the-large remains understudied, hindering the full integration of multi-stage programming support into existing languages, and limiting the effective use of staging in large programs. We take steps to remedy the situation by studying the extension of MacoCaml, a recent OCaml extension that supports compile-time code generation via macros and quotations , with module functors, the key mechanism in OCaml for assembling program components into larger units. We discuss design choices related to evaluation order, formalize our calculus via elaboration, and show that the design enjoys key metatheoretical properties: syntactic type soundness, elaboration soundness, and phase distinction. We believe that this study lays a foundation for the continued exploration and implementation of the OCaml macro system.

Parallel Algebraic Effect Handlers

Algebraic effect handlers support composable and structured control-flow abstraction. However, existing designs of algebraic effects often require effects to be executed sequentially. This paper studies parallel algebraic effect handlers. In particular, we formalize λ p , a lambda calculus which models two key features, effect handlers and parallelizable computations, the latter of which takes the form of a for expression, inspired by the Dex programming language. We present various interesting examples expressible in our calculus. To show that our design can be implemented in a type-safe way, we present a higher-order polymorphic lambda calculus F p that extends λ p with a lightweight value dependent type system, and prove that F p preserves the semantics of λ p and enjoys syntactic type soundness. Lastly, we provide an implementation of the language design as a Haskell library, which mirrors both λ p and F p and reveals new connections to free applicative functors. All examples presented can be encoded in the Haskell implementation. We believe this paper is the first to study the combination of user-defined effect handlers and parallel computations, and it is our hope that it provides a basis for future designs and implementations of parallel algebraic effect handlers.

Assessments of prostate cancer cell functions highlight differences between a pan-PI3K/mTOR inhibitor, gedatolisib, and single-node inhibitors of the PI3K/AKT/mTOR pathway.

Metastatic castration-resistant prostate cancer (mCRPC) is characterized by loss of androgen receptor (AR) sensitivity and oncogenic activation of the PI3K/AKT/mTOR (PAM) pathway. Loss of the PI3K regulator PTEN is frequent during prostate cancer (PC) initiation, progression, and therapeutic resistance. Co-targeting the PAM/AR pathways is a promising mCRPC treatment strategy but is hampered by reciprocal negative feedback inhibition or feedback relief. Most PAM inhibitors selectively spare (or weakly inhibit) one or more key nodes of the PAM pathway, potentiating drug resistance depending on the PAM pathway mutation status of patients. We posited that gedatolisib, a uniformly potent inhibitor of all class I PI3K isoforms, as well as mTORC1 and mTORC2, would be more effective than inhibitors targeting single PAM pathway nodes in PC cells. Using a combination of functional and metabolic assays, we evaluated a panel of PC cell lines with different PTEN/PIK3CA status for their sensitivity to multi-node PAM inhibitors (PI3K/mTOR: gedatolisib, samotolisib) and single-node PAM inhibitors (PI3Kα: alpelisib; AKT: capivasertib; mTOR: everolimus). Gedatolisib induced anti-proliferative and cytotoxic effects with greater potency and efficacy relative to the other PAM inhibitors, independent of PTEN/PIK3CA status. The superior effects of gedatolisib were likely associated with more effective inhibition of critical PAM-controlled cell functions, including cell cycle, survival, protein synthesis, oxygen consumption rate, and glycolysis. Our results indicate that potent and simultaneous blockade of all class I PI3K isoforms, mTORC1, and mTORC2 could circumvent PTEN-dependent resistance. Gedatolisib, as a single agent and in combination with other therapies, reported promising preliminary efficacy and safety in various solid tumor types. Gedatolisib is currently being evaluated in a Phase 1/2 clinical trial in combination with darolutamide in patients with mCRPC previously treated with an AR inhibitor, and in a Phase 3 clinical trial in combination with palbociclib and fulvestrant in patients with HR+/HER2- advanced breast cancer.

Efficacy and Prolonged Safety of Haemophilus influenzae Type b Conjugate Vaccines.

The purpose of this study was to find data proving the influence of the Haemophilus influenzae type b (Hib) conjugate vaccination on the frequency of invasive Hib illness. A systematic literature search was conducted on the PubMed database to identify peerreviewed publications pertaining to the epidemiology of Haemophilus influenzae meningitis, both before and after the introduction of Haemophilus influenzae type b (Hib) conjugate vaccines. The search query employed a combination of relevant keywords, including "invasive," "Haemophilus," "influenzae," "meningitis," and specific serotype b (Hib). Additionally, terms related to epidemiology, burden, risk factors, impact, Hib vaccine, Hib conjugate vaccine, combination vaccine, vaccine production, efficacy, immunisation coverage, surveillance, review, clinical aspects, outcomes, and various age groups (adults and children) were incorporated. The search encompassed articles published till now. Subsequently, relevant research papers concerning Haemophilus influenzae meningitis were subjected to a comprehensive review and analysis. The Hib conjugate vaccination has shown to be extremely effective when administered to the entire population. However, changes to the immunisation protocol appear to be required in order to effectively manage invasive Hib illness.

Rancang Bangun Aplikasi Pendeteksi Golongan Darah Dan Rhesus Berbasis Internet Of Things

The rapid advancement of technology in today's world has led to significant progress in various aspects of human life, including healthcare. Nowadays, numerous advanced medical devices are being created to facilitate healthcare services. Health is a crucial element in human life, which is why regular monitoring through laboratory tests is essential. Blood type and Rh factor are critical pieces of information in the medical field, especially for blood transfusions and specific medical treatments. However, determining a person's blood type still relies on manual methods, requiring experienced professionals and a considerable amount of time to analyze blood samples. To address this challenge, an Internet of Things (IoT)-based blood type and Rh factor detection device is being developed.The main objective of this research is to design and implement an efficient, fast, and user-friendly device for detecting blood type and Rh factor using IoT technology. Furthermore, this device aims to simplify data storage after conducting a large number of blood type checks, eliminating the need for repeated testing. The creation of this blood type and Rh factor detection device requires several components, including the WiFi module ESP8266, Arduino Uno, and a light sensor built with LDR components. The results will be displayed on a 16x2 LCD and the data obtained from the testing process will be sent to a designated web page. This data will be stored in a MySQL database and subsequently presented on a website.